How to check port occupancy in Linux

How to check the port occupation in Linux: Use [lsof -i port number or netstat -tunlp|grep port number]. Both commands can check what process the port is occupied by.

The operating environment of this tutorial: linux7.3 system, DELL G3 computer.

How to check port occupancy in Linux:

1. Commonly used commands:

(1) lsof -i port number

(2) netstat -tunlp|grep port number

Both commands can check what process the port is occupied.

2. lsof -i is used to display the conditions of processes that meet the conditions. lsof (list open files) is a tool that lists open files in the current system. Execute the lsof -i command as the root user, as shown below

The meaning of each column output by lsof is:

• COMMAND: The name of the process or the method of starting the process

• PID: process id

• USER: process owner

• FD: file descriptor

• TYPE: Protocol type

• DEVICE: Port number

• SIZE/OFF: Offset

• NODE: protocol name

• NAME: node name

3. lsof -i: Port number, used to check the occupancy of a certain port, for example, to check the usage of port 22, lsof -i:22, as shown below

4. netstat -tunlp is used to display tcp, udp ports and processes and other related conditions. As shown in the figure below

, t, u, n, l, p in the command have different meanings:

-t Only displays those related to tcp

-u Only displays those related to udp

-n No time limit alias, can display all numbers converted into numbers

-l Only displays those in the Listen state

-p Displays the program names that establish these connections

5, netstat -tunlp|grep port number, used to check the process status of the specified port number, such as checking the status of port 22, netstat -tunlp|grep 22, as shown below

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